This
image taken inside Cairn T shows the shaped beam of equinox
sunlight illuminating the back stone. The symbol on the top left
of the illuminated area clearly represents the sun and the symbols with the
horizontal markings may be measuring scales.

Tim
O'Brien in his book Light Years Ago states "It
would appear that the construction of Cairn T was specifically
designed to cleverly fashion a beam of light from the rising and
early risen sun around the time of the equinoxes to define the four
year equinox or leap year cycle."

Light
Years Ago by Tim O'Brien shows that the symbols of the sun
engraved on the backstone of Cairn T at Loughcrew are precisely
positioned to measure solar movement. A beam of light from the rising
sun around the time of the March and September equinoxes is mapped on
the backstone.

Boyne Valley Tours

Private Tour with pick up and return to your accommodation.
Newgrange World Heritage site, the 10th century High Crosses at Monasterboice,
Hill of Tara the seat of the High Kings, Bective Abbey and Trim Castle
the largest Norman castle in Ireland
More ...